The present invention relates to object detection systems, and more particularly relates to systems for detecting objects, including personnel, in the aisles of a moveable unit storage system.
Moveable unit storage systems incorporate a plurality of storage units, such as shelves, racks and the like. These units are arranged to move relative to one another so as to open and close aisles between different pairs of adjacent storage units. Such systems include two end units spaced apart from one another in a movement direction and middle units disposed in a work area, between the end units. Typically, the middle units are mounted on wheels and guided by tracks so that they can only move in preselected movement directions towards and away from the end units. The distance between the end units is sufficient to accommodate all of the middle units plus one or a few aisles. If an aisle exists between two middle units or between one middle unit and one end unit, one middle unit can be moved into the aisle, thus closing the original aisle and opening a new aisle between the moved middle unit and another unit. Systems of this nature are particularly advantageous because they conserve space, and hence conserve all of the costs associated with building construction and operation. The user can still have full aisle access to all of the storage units, but need allocate building space for only one aisle or a few aisles.
In the larger systems of this nature, the storage units are moved by powered devices such as electric motors under manual or automatic control. In these systems, safety devices are employed to avoid actuating the units to close an aisle while a person is in the aisle. One common safety device employs mechanical bumpers extending along the length of each storage unit, i.e., along the storage unit in the direction transverse to the movement directions. At least one such bumper is provided between each pair of adjacent storage units. Each bumper is linked to electrical switches. If the bumper encounters a person or other object in the aisle as the storage units move toward one another to close that aisle, the bumper trips the electrical switches. The switches in turn are connected so that when tripped, they will stop the closing motion, as by interrupting current to the driving motors or by applying brakes or catches to the moving elements.
Bumper-based safety systems are effective, but have certain drawbacks. The safety system will not stop the moving units until one or both of the units have come close enough to the person within the aisle for the bumpers to touch him or her. Even though the person is not endangered, he or she may be frightened by the moving units. As disclosed, for example, in U.S. Pat. Nos. 4,307,922 and 4,783,618, a mechanical bumper system may be supplemented with electronic proximity sponsors on each unit, such as heat-sensitive or capacitive sensors. Typically, only relatively few sensors are disposed along the length of each storage unit, so that each sensor must provide protection for a substantial portion of the adjacent aisle. In a variant of that approach, disclosed in U.S. Pat. No. 5,121,975, each storage unit is provided with a lamp and photocell. These are mounted on a lengthwise edge of the unit so that the lamp projects a beam in the lengthwise direction along the edge of the unit to the photocell.
The beam is interrupted by a person or object in the aisle as the unit moves toward the next adjacent unit to close the aisle. Yet another system, disclosed in U.S. Pat. No. 5,160,190, mounts a small radar device to each storage unit so that the radar device will point downwardly, into the aisle when such storage unit is adjacent an open aisle.
All of the aforementioned systems are costly and complex in that they require components mounted to each of the individual storage units. The number of such components increases proportionately with the number of storage units in the system. The complexity and possibility for failure of the system increase exponentially with the increasing numbers of components. Although such systems can be arranged for "fail safe" operation, so that failure of any single component locks the system rather than allowing the system to operate in a potentially dangerous or frightening mode, such fail safe operation does not provide a complete solution to the problem. Productivity can be substantially hampered by failure of the safety system, leading to attempts to disable or circumvent the safety system. Yet another system mentioned in passing in the aforementioned '190 patent, utilizes moveable floor sections and switches actuated by depression of such moveable floor sections when a person stands upon them. As noted in the '190 patent, this arrangement has a substantial drawback in that it requires installation of special moveable flooring and switches associated therewith.
Another drawback encountered in many of the prior systems is that the same often are arranged to detect persons or objects only at or adjacent the floor level, i.e., at the bottoms of the storage units. For example, as disclosed in the aforementioned '975 patent, the lamp and photocell are arranged along the bottom edge of each unit. A person working in an aisle in such a storage system can climb up along the storage unit as, for example, to reach an object on a high shelf. This may occur even where such practice is expressly prohibited by the owner of the system. Accordingly, it would be desirable if the safety system could effectively inhibit closure of an aisle when an individual is within the aisle even where the individual has climbed above floor level.
Thus, there have been substantial unmet needs heretofore for improvements in storage systems with moveable storage units, and there have been similar needs for improvement in safety systems for this and other applications.